Popular gaming forums NeoGaf and Resetera only allow signups from paid email accounts. All free and temporary email providers are banned to discourage trolls / forum raids / alt accounts.

Ars Technica is one you can test I believe. I think I had to register with Gmail and put in a support ticket to ask them to change it to my real email. I use Fastmail, not a selfhosted setup or anything, some services absolutely have a domain allowlist for email signup.